Method and apparatus for revascularizing a coronary vessel with an implant having a tapered myocardial leg

ABSTRACT

A method for revascularizing a coronary vessel with a conduit through the heart wall having a diameter transition in the myocardial leg, wherein blood flow is in the direction of transition from larger to smaller diameter. A method for revascularizing a coronary vessel using an implant with a myocardial leg having a maximum cross-sectional area proximate a first end, and inserting the first end through the myocardium into a heart chamber so that the implant directs blood flow into the coronary vessel. A transmyocardial implant with a myocardial leg including point of minimum diameter and a first end with a larger diameter, and a vessel leg in fluid communication with the myocardial leg.

I. CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation of U.S. Ser. No.09/326,819, filed Jun. 7, 1999, which is a divisional of U.S. Ser. No.08/882,397, filed Jun. 25, 1997, which issued as U.S. Pat. No. 5,944,019on Aug. 31, 1999, which is a continuation-in-part of U.S. Ser. No.08/689,773, filed Aug. 13, 1996, which issued as U.S. Pat. No. 5,755,682on May 26, 1998.

II. BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to a method and apparatusfor performing a coronary artery bypass procedure. More particularly,the present invention performs a coronary artery bypass by providing adirect flow path from a heart chamber to the coronary artery. Thepresent invention is suitable for a number of approaches including anopen-chest approach (with and without cardiopulmonary bypass), aclosed-chest approach under direct viewing and/or indirect thoracoscopicviewing (with and without cardiopulmonary bypass), and an internalapproach through catheterization of the heart and a coronary arterialvasculature without direct or indirect viewing (with and withoutcardiopulmonary bypass).

[0004] 2. Description of the Prior Art

[0005] A. Coronary Artery Disease

[0006] Coronary artery disease is the leading cause of premature deathin industrialized societies. The mortality statistics tell only aportion of the story. Many who survive face prolonged suffering anddisability.

[0007] Arteriosclerosis is “a group of diseases characterized bythickening and loss of elasticity of arterial walls.” Dorland'SIllustrated Medical Dictionary 137 (27th ed. 1988). Arteriosclerosis“comprises three distinct forms: atherosclerosis, Monckeberg'sarteriosclerosis, and arteriolosclerosis.” Id.

[0008] Coronary artery disease has been treated by a number of means.Early in this century, the treatment for arteriosclerotic heart diseasewas largely limited to medical measures of symptomatic control. Evolvingmethods of diagnosis, coupled with improving techniques ofpost-operative support, now allow the precise localization of theblocked site or sites and either their surgical re-opening or bypass.

[0009] B. Angioplasty

[0010] The re-opening of the stenosed or occluded site can beaccomplished by several techniques. Angioplasty, the expansion of areasof narrowing of a blood vessel, is most often accomplished by theintravascular introduction of a balloon-equipped catheter. Inflation ofthe balloon causes mechanical compression of the arteriosclerotic plaqueagainst the vessel wall.

[0011] Alternative intravascular procedures to relieve vessel occlusioninclude atherectomy, which results in the physical desolution of plaqueby a catheter equipped with a removal tool (e.g., a cutting blade orhigh-speed rotating tip). Any of these techniques may or may not befollowed by the placement of a mechanical support (i.e., a stent) whichphysically holds open the artery.

[0012] Angioplasty, and the other above-described techniques (althoughless invasive than coronary artery bypass grafting) are fraught with acorrespondingly greater failure rate due to intimal proliferation.Contemporary reports suggest re-stenosis is realized in as many as 25 to55 percent of cases within 6 months of successful angioplasty. See BojanCercek et al., 68 Am. J. Cardiol. 24C-33C (Nov. 4, 1991). It ispresently believed stenting can reduce the re-stenosis rate.

[0013] A variety of approaches to delay or prevent re-blockage haveevolved. One is to stent the site at the time of balloon angioplasty.Another is pyroplasty, where the balloon itself is heated duringinflation. As these alternative techniques are relatively recentinnovations, it is too early to tell just how successful they will be inthe long term. However, because re-blockage necessitates the performanceof another procedure, there has been renewed interest in the clearlylonger-lasting bypass operations.

[0014] C. Coronary Artery Bypass Grafting

[0015] i. Outline of Procedure

[0016] The traditional open-chest procedure for coronary artery bypassgrafting requires an incision of the skin anteriorly from nearly theneck to the navel, the sawing of the sternum in half longitudinally, andthe spreading of the ribcage with a mechanical device to affordprolonged exposure of the heart cavity. If the heart chamber or a vesselis opened, a heart-lung, or cardiopulmonary bypass, procedure is usuallynecessary.

[0017] Depending upon the degree and number of coronary vesselocclusions, a single, double, triple, or even greater number of bypassprocedures may be necessary. Often each bypass is accomplished by thesurgical formation of a separate conduit from the aorta to the stenosedor obstructed coronary artery at a location distal to the diseased site.

[0018] ii. Limited Number of Available Grafts

[0019] The major obstacles to coronary artery bypass grafting includeboth the limited number of vessels that are available to serve asconduits and the skill required to effect complicated multiple vesselrepair. Potential conduits include the two saphenous veins of the lowerextremities, the two internal thoracic (mammary) arteries under thesternum, and the single gastroepiploic artery in the upper abdomen.

[0020] Newer procedures using a single vessel to bypass multiple siteshave evolved. This technique has its own inherent hazards. When a singlevessel is used to perform multiple bypasses, physical stress (e.g.,torsion) on the conduit vessel can result. Such torsion is particularlydetrimental when this vessel is an artery. Unfortunately, attempts atusing artificial vessels or vessels from other species (xenografts), orother non-related humans (homografts) have been largely unsuccessful.See LUDWIG K. Von Segesser, Arterial Grafting For MyocardialRevascularization: Indications, Surgical Techniques and Results 38-39(1990)

[0021] While experimental procedures transplanting alternative vesselscontinue to be performed, in general clinical practice, there are fivevessels available to use in this procedure over the life of a particularpatient. Once these vessels have been sacrificed or affected by disease,there is little or nothing that modem medicine can offer. It isunquestionable that new methods, not limited by the availability of suchconduit vessels, are needed.

[0022] iii. Trauma of Open Chest Surgery

[0023] In the past, the normal contractions of the heart have usuallybeen stopped during suturing of the bypass vasculature. This can beaccomplished by either electrical stimulation which induces ventricularfibrillation, or through the use of certain solutions, calledcardioplegia, which chemically alter the electrolyte milieu surroundingcardiac muscles and arrest heart activity.

[0024] Stoppage of the heart enhances visualization of the coronaryvessels and eliminates movement of the heart while removing the need forblood flow through the coronary arteries during the procedure. Thisprovides the surgeon with a “dry field” in which to operate and create afunctional anastomosis.

[0025] After the coronary artery bypass procedure is completed,cardioplegia is reversed, and the heart electrically stimulated ifnecessary. As the heart resumes the systemic pumping of blood, thecardiopulmonary bypass is gradually withdrawn. The separated sternalsections are then re-joined, and the overlying skin and saphenous donorsite or sites (if opened) are sutured closed.

[0026] The above-described procedure is highly traumatic. Immediatepost-operative complications include infection, bleeding, renal failure,pulmonary edema and cardiac failure. The patient must remain intubatedand under intensive post-operative care. Narcotic analgesia is necessaryto alleviate the pain and discomfort.

[0027] iv. Post-operative Complications

[0028] Once the immediate post-surgical period has passed, the mosttroubling complication is bypass vessel re-occlusion. This has been aparticular problem with bypass grafting of the left anterior descendingcoronary artery when the saphenous vein is employed.

[0029] Grafting with the internal thoracic (internal mammary) arteryresults in a long-term patency rate superior to saphenous vein grafts.This is particularly the case when the left anterior descending coronaryartery is bypassed. Despite this finding, some cardiothoracic surgeonscontinue to utilize the saphenous vein because the internal thoracicartery is smaller in diameter and more fragile to manipulation. Thismakes the bypass more complex, time-consuming, and technicallydifficult. Additionally, there are physiological characteristics of anartery (such as a tendency to constrict) which increase the risk ofirreversible damage to the heart during the immediate period ofpost-surgical recovery.

[0030] Once the patient leaves the hospital, it may take an additionalfive to ten weeks to recover completely. There is a prolonged periodduring which trauma to the sternum (such as that caused by an automobileaccident) can be especially dangerous. The risk becomes even greaterwhen the internal thoracic artery or arteries, which are principlesuppliers of blood to the sternum, have been ligated and employed asbypass vessels.

[0031] v. Less Invasive Procedures

[0032] Due to the invasive nature of the above technique, methods havebeen devised which employ contemporary thoracoscopic devices andspecially-designed surgical tools to allow coronary artery bypassgrafting by closed-chest techniques. While less invasive, all but themost recent closed-chest techniques still require cardiopulmonarybypass, and rely on direct viewing by the surgeon during vascularanastomoses.

[0033] These methods require a very high level of surgical skilltogether with extensive training. In such situations, the suturing ofthe bypassing vessel to the coronary artery is performed through a spacecreated in the low anterior chest wall by excising the cartilaginousportion of the left fourth rib. Also, as they continue to rely on theuse of the patient's vessels as bypass conduits, the procedures remainlimited as to the number of bypasses which can be performed. Because ofthese issues, these methods are not yet widely available.

[0034] vi. Objectives for Improved Bypass Procedures

[0035] In view of the above, it is desirable to provide other methods bywhich adequate blood flow to the heart can be re-established and whichdo not rely on the transposition of a patient's own arteries or veins.Preferably, such methods will result in minimal tissue injury.

[0036] While the attainment of the foregoing objectives through an openchest procedure would, by themselves, be a significant advance, it isalso desirable if such methods would also be susceptible to surgicalprocedures which do not require opening of the chest by surgicalincision of the overlying skin and the division of the sternum. Suchmethods would not require surgical removal of cartilage associated withthe left fourth rib, would not require the surgical transection of oneor both internal thoracic arteries, would not require the surgicalincision of the skin overlying one or both lower extremities, and wouldnot require the surgical transection and removal of one or bothsaphenous veins. In both an open and closed chest approach, it is alsobe desirable if such methods could be performed without stoppage of theheart and without cardiopulmonary bypass. However, attainment of theforegoing objectives in a procedure requiring cardiopulmonary bypasswould still be a significant advance in the art.

[0037] vii. References for Prior Art Techniques

[0038] The conventional surgical procedures (such as those describedabove) for coronary artery bypass grafting using saphenous vein orinternal thoracic artery via an open-chest approach have been describedand illustrated in detail. See generally Stuart W. Jamieson,Aortocoronary Saphenous Vein Bypass Grafting, in Rob & Smith's OperativeSurgery: Cardiac Surgery, 454-470 (Stuart W. Jamieson & Norman E.Shumway eds., 4th ed. 1986); Ludwig K. Von Segesser, Arterial Graftingfor Myocardial Revascularization: Indications, Surgical Techniques andResults 48-80 (1990). Conventional cardiopulmonary bypass techniques areoutlined in Mark W. Connolly & Robert A. Guyton, Cardiopulmonary BypassTechniques, in Hurst'S the Heart 2443-450 (Robert C. Schlant & R. WayneAlexander eds., 8th ed. 1994). Coronary artery bypass grafting utilizingopen-chest techniques but without cardiopulmonary bypass is described inEnio Buffolo et al., Coronary Artery Bypass Grafting WithoutCardiopulmonary Bypass, 61 Ann. Thorac. Surg. 63-66 (1996).

[0039] Some less conventional techniques (such as those described above)are performed by only a limited number of appropriately skilledpractitioners. Recently developed techniques by which to perform acoronary artery bypass graft utilizing thoracoscopy andminimally-invasive surgery, but with cardiopulmonary bypass, aredescribed and illustrated in Sterman et al., U.S. Pat. No. 5,452,733(1995). An even more recent coronary artery bypass procedure employingthoracoscopy and minimally-invasive surgery, but without cardiopulmonarybypass, is described and illustrated by Tea E. Acuff et al., MinimallyInvasive Coronary Artery Bypass Grafting, 61 Ann. Thorac. Surg. 135-37(1996).

[0040] D. Bypass With Direct Flow From Left Ventricle

[0041] 1. Summary of Procedures

[0042] Certain methods have been proposed to provide a direct blood flowpath from the left ventricle directly through the heart wall to thecoronary artery. These are described in U.S. Pat. No. 5,429,144 datedJul. 4, 1995; U.S. Pat. No. 5,287,861 dated Feb. 22, 1994; and U.S. Pat.No. 5,409,019 dated Apr. 25, 1995 (all to Wilk). All of these techniquesinclude providing a stent in the heart wall to define a direct flow pathfrom the left ventricle of the heart to the coronary artery.

[0043] As taught in each of the above-referenced patents, the stent isclosed during either systole or diastole to block return flow of bloodfrom the coronary artery during the heart's cycle. For example, the '861patent teaches a stent which collapses to a closed state in response toheart muscle contraction during systole. The '019 patent (particularlyFIGS. 7A and 7B) teaches a rigid stent (i.e., open during systole) witha one-way valve which closes during diastole to block return flow ofblood from the coronary artery.

[0044] ii. Problems

[0045] The interruption of blood flow during either diastole or systoleis undesirable since such interruption can result in areas of stagnantor turbulent blood flow. Such areas of stagnation can result in clotformation which can result in occlusion or thrombi breaking lose. Suchthrombi can be carried to the coronary arteries causing one or moreareas of cardiac muscle ischemia (myocardial infarction) which can befatal. Further, the teachings of the aforementioned patents direct bloodflow with a substantial velocity vector orthogonal to the axis of thecoronary artery. Such flow can damage the wall of the coronary artery.

[0046] Providing direct blood flow from the left ventricle of thecoronary artery has been criticized. For example, Munro et al., ThePossibility of Myocardial Revascularization By Creation of a LeftVentriculocoronary Artery Fistula, 58 Jour. Thoracic and CardiovascularSurgery, 25-32 (1969) shows such a flow path in FIG. 1. Noting a fall incoronary artery flow and other adverse consequences, the authorsconcluded “that operations designed to revascularize the myocardiumdirect from the cavity of the left ventricle make the myocardiumischemic and are unlikely to succeed.” Id at 31.

[0047] Notwithstanding the foregoing problems and scholarly criticism,and as will be more fully described, the present invention is directedto an apparatus and method for providing a direct blood flow path from aheart chamber to a coronary artery downstream of an obstruction. Counterto the teachings of the prior art, the present invention providessubstantial net blood flow to the coronary artery.

[0048] E. Additional Techniques

[0049] Methods of catheterization of the coronary vasculature,techniques utilized in the performance of angioplasty and atherectomy,and the variety of stents in current clinical use have been summarized.See generally Bruce F. Waller & Cass A. Pinkerton, The Pathology ofInterventional Coronary Artery Techniques and Devices, in 1 Topol'sTextbook of Interventional Cardiology 449-476 (Eric J. Topol ed., 2nded. 1994); see also David W. M. Muller & Eric J. Topol, Overview ofCoronary Athrectomy, in 1 Topol's Textbook of Interventional Cardiologyat 678-684; see also Ulrich Sigwart, An Overview of IntravascularStents: Old & New, in 2 Topol's Textbook of Interventional Cardiology at803-815.

[0050] Direct laser canalization of cardiac musculature (as opposed tocanalization of coronary artery feeding the cardiac musculature) isdescribed in Peter Whittaker et al., Transmural Channels Can ProtectIschemic Tissue: Assessment of Long-term Myocardial Response toLaser-and Needle-Made Channels, 94(1) Circulation 143-152 (Jan. 1,1996). Massimo et al., Myocardial Revascularization By a New Method ofCarrying Blood Directly From The Left Ventricular Cavity Into TheCoronary Circulation, 34 Jour. Thoracic Surgery 257-264 (1957) describesa T-shaped tube placed within the ventricular wall and protruding intothe cavity of the left ventricle. Also, Vineberg et al., Treatment ofAcute Myocardial Infarction By Endocardial Resection, 57 Surgery 832-835(1965) teaches forming a large opening between the left ventricularlumen and the sponge-like network of vessels lying within themyocardium.

III. SUMMARY OF THE INVENTION

[0051] The present invention relates to a method for revascularizing acoronary vessel with a conduit through the heart wall having a diametertransition in the myocardial leg, wherein blood flow is in the directionof transition from larger to smaller diameter. The present inventionfurther relates to revascularizing a coronary vessel using an implantwith a transmyocardial leg having a maximum cross-sectional areaproximate a first end, and inserting the first end through themyocardium into a heart chamber so that the implant directs blood flowinto the coronary vessel. The present invention also relates to atransmyocardial implant with a myocardial leg including point of minimumdiameter and a first end with a larger diameter, and a vessel leg influid communication with the myocardial leg.

IV. BRIEF DESCRIPTION OF THE DRAWINGS

[0052]FIG. 1A is a right, front and top perspective view of an L-shapedconduit for use in the present invention;

[0053]FIG. 1B is a side elevation view of the apparatus of FIG. 1A shownpartially in section to reveal an optional bi-directional flow regulatorlocated in a lumen of an anchor arm of the conduit;

[0054]FIG. 1C is a side elevation view of a conduit similar to that ofFIG. 1A showing the addition of a capacitance pressure reservoir as analternative embodiment;

[0055]FIG. 2A is a right, front and top perspective view of a T-shapedconduit according to the present invention;

[0056]FIG. 2B is a side elevation view of the conduit of FIG. 2A shownpartially in section to reveal an optional bi-directional flow regulatorlocated in a lumen of an anchor arm of the conduit;

[0057]FIG. 2C is a side elevation view of the conduit of FIG. 2A shownpartially in section to reveal one optional bi-directional flowregulator located in the lumen of the anchor arm of the conduit, andanother optional bi-directional flow regulator located in anintracoronary arm of the conduit;

[0058]FIG. 2D is a side elevation view of a conduit similar to that ofFIG. 2A showing the addition of a capacitance pressure reservoir as analternative embodiment;

[0059]FIG. 3A is a partial side elevation view of a conduit similar tothat of FIGS. 1A and 2A shown partially in section to reveal a flexibleanchor arm with rigid rings ensheathed in a flexible covering as analternative embodiment;

[0060]FIG. 3B is a partial side elevation view of a conduit similar tothat of FIG. 3A shown in section in an extended form;

[0061]FIG. 3C is a partial side elevation view of a conduit similar tothat of FIG. 3A shown in section in a compressed form;

[0062]FIG. 4 is an anterior view of a human chest which is incisedlongitudinally to reveal a dissected pericardium and mediastinalcontents;

[0063]FIG. 5 is a magnified view of an area circled 200 in FIG. 4illustrating a longitudinally incised coronary artery;

[0064]FIG. 6 is a partial external perspective view of a transverselysectioned coronary artery and heart wall illustrating a channel leadingfrom a lumen of a coronary artery and into a chamber of the heartaccording to the method of the present invention;

[0065]FIG. 7 is a partial external perspective view of a transverselysectioned coronary artery and heart wall illustrating the partialplacement of one embodiment of the conduit of the present invention intothe incised coronary artery and formed channel illustrated in FIG. 6;

[0066]FIG. 8 is a partial external perspective view of a transverselysectioned coronary artery and heart wall illustrating the completedplacement of one embodiment of the conduit of the present invention intothe incised coronary artery and formed channel illustrated in FIG. 6;

[0067]FIG. 9 is a partial external perspective view of a suturedcoronary artery and phantom view of the conduit of the presentinvention;

[0068]FIG. 10 is a schematic illustration of the use of an endovascularcatheter to catheterize the patient's coronary artery;

[0069]FIG. 11A is a cutaway side elevation view of the coronary arteryof the bypass procedure illustrating an intravascular catheter withdistally-located stent prior to inflation of a catheter balloonunderlying the stent;

[0070]FIG. 11B is a cutaway side elevation view of the coronary arteryof the bypass procedure illustrating the intravascular catheter withdistally-located stent following inflation of the catheter balloonunderlying the stent;

[0071]FIG. 11C is a cutaway side elevation view of a coronary arteryillustrating the stent seated to the walls of the coronary artery andthe catheter partially withdrawn following deflation of the catheterballoon;

[0072]FIG. 12 is a schematic illustration with the heart in partialcutaway of the use of an endovascular catheter to catheterize thepatient's left ventricle.

[0073]FIG. 13A is a cutaway view of the left ventricle and a partialcutaway view of the coronary artery with seated stent illustrating theformation of a channel into the wall of the left ventricle;

[0074]FIG. 13B is a cutaway view of the left ventricle and a partialcutaway view of the coronary artery with seated stent illustrating acompleted channel through the wall of the left ventricle and deep wallof the coronary artery at the chosen bypass site;

[0075]FIG. 14A is a cross-sectioned view of the left ventricle and apartial cutaway view of the coronary artery with seated stentillustrating the placement of the second intraventricular catheterwithin the formed channel;

[0076]FIG. 14B is a cross-sectioned view of the left ventricle and apartial cutaway view of the coronary artery with seated stentillustrating a blockage of the formed channel by the re-inflated balloonof the intracoronary catheter;

[0077]FIG. 14C is a cross-sectioned view of the left ventricle and apartial cutaway view of the coronary artery with seated stentillustrating an inflation of the balloon located on the distal end ofthe intraventricular catheter and the seating of an overlyingspiral-shaped device against the walls of the formed channel;

[0078]FIG. 14D is a cross-sectioned view of the left ventricle and apartial cutaway view of the coronary artery with seated stentillustrating the device in its locked cylindrical shape seated againstthe channel walls and the partially withdrawn second intraventricularcatheter;

[0079]FIG. 15A is a right anterior superior perspective view of thedevice placed within the formed channel in its spiral shape;

[0080]FIG. 15B is a right anterior superior perspective view of thedevice placed within the formed channel in its cylindrical form;

[0081]FIG. 16 is a cross-sectional view of an interlocking mechanism ofthe device of FIGS. 15A and 15B in its locked position;

[0082]FIG. 17A is a cross-sectioned view of the left ventricle and apartial cutaway view of the coronary artery, with the device shown inFIGS. 15A and 15B seated within the formed channel, illustrating theintroduction of a third intraventricular catheter into the formedchannel;

[0083]FIG. 17B is a cross-sectioned view of the left ventricle and apartial cutaway view of the coronary artery, with the device shown inFIGS. 15A and 15B seated within the formed channel, illustrating atongue and groove interlocking of the bi-directional flow regulatorequipped device to the device seated within the formed channel;

[0084]FIG. 18A is a schematic longitudinal cross-sectional view of abi-directional flow regulator shown in a fill flow position.

[0085]FIG. 18B is the view of FIG. 18A with the bi-directional flowregulator shown in a reduced flow position;

[0086]FIG. 18C is a transverse cross-sectional view of thebi-directional flow regulator of FIG. 18B;

[0087]FIG. 19A is a schematic cross-section longitudinal view of analternative embodiment of a bi-directional flow regulator shown in afull flow position;

[0088]FIG. 19B is the view of FIG. 19A showing the bi-directional flowregulator in a reduced flow position;

[0089]FIG. 19C is a transverse cross-sectional view of thebi-directional flow regulator of FIG. 19B;

[0090]FIG. 20 is a schematic longitudinal cross-sectional view of achannel defining conduit with an alternative embodiment tapered anchorarm;

[0091]FIG. 21 is a schematic longitudinal cross-sectional view of theconduit of FIG. 1A in place in a coronary artery;

[0092]FIG. 22 is a schematic longitudinal cross-sectional view of a testconduit for animal testing of the invention; and

[0093]FIG. 23 is a schematic longitudinal cross-sectional view of aconduit in place in a coronary artery illustrating a deflecting shieldto protect the coronary artery.

V. DESCRIPTION OF THE PREFERRED EMBODIMENT

[0094] With reference now to the various drawing figures in whichidentical elements are numbered identically throughout, a description ofthe preferred embodiment of the present invention and variousalternative embodiments will now be provided.

[0095] A. Detailed Summary of the Preferred Embodiment

[0096] The invention departs from the traditional bypass approach.Rather then providing an alternative pathway for blood to flow from anaorta to a coronary artery, the invention provides a blood flow pathleading directly from a chamber of a heart to a coronary artery at asite downstream from the stenosis or occlusion. Unlike U.S. Pat. Nos.5,429,144; 5,287,861 and 5,409,019 and contrary to the teachings ofthese patents, the ventricular-to-coronary artery blood flow pathremains open during both diastole and systole. The surgical placement ofthe apparatus of the present invention establishes this alternativepathway. Also, and as will be more fully described, the inventionincludes means for protecting the coronary artery from directimpingement of high velocity blood flow.

[0097] While the invention will be described in multiple embodiments andwith the description of various surgical procedures for practicing theinvention, it will be appreciated that the recitation of such multipleembodiments is done for the purpose of illustrating non-limitingexamples of multiple forms which the present invention may take.

[0098] The presently preferred embodiment is illustrated in FIG. 1A asan L-shaped conduit 10′ with an intracoronary arm 14′ to reside in thecoronary artery (and opening downstream of an occlusion). The conduit10′ has an anchor arm 12′ extending through the heart wall with anopening 12 a′ in communication with the interior of the left ventricle.

[0099] While various minimally invasive surgical procedures aredescribed with respect to alternative embodiments, the presentlypreferred embodiment places the conduit 10′ into a coronary arterythrough an open-chest approach to be described in greater detail withreference to FIGS. 4-9. While minimally invasive procedures aredesirable, an open chest procedure is presently preferred due to thealready large number of physicians trained and skilled in suchprocedures thus making the benefits of the present invention morerapidly available to patients who currently lack effective treatment.

[0100] While the various embodiments (including the presently preferredembodiment of FIG. 1A) will be described in greater detail, apreliminary description of the invention and its method of use will nowbe given with reference to FIG. 21 to facilitate an understanding of adetailed description of the invention and the alternate embodiments.

[0101]FIG. 21 is a schematic cross-sectional view of a conduit 10′ ofFIG. 1A placed within a coronary artery 30. Coronary artery 30 has alower surface 40 residing against an external surface of a heart wall 42surrounding the left ventricle 44.

[0102] The wall 36 of the artery 30 defines an artery lumen 48 throughwhich blood flows in the direction of arrow A. In the view of FIG. 21,an obstruction 34 is shown within the lumen 48. The obstruction 34 actsto reduce the volume of blood flow along the direction of arrow A.

[0103] The conduit 10′ is a rigid, L-shaped tube having an anchor arm12′ with a longitudinal axis X-X and an opening 12 a′ at an axial end.The conduit 10′ may be any suitable device (e.g., rigid tube, latticestent, etc.) for defining and maintaining a fluid pathway duringcontraction of the heart.

[0104] The conduit 10′ has an intracoronary arm 14′ with a longitudinalaxis Y-Y and an opening 14 a′ at an axial end. Both of arms 12′, 14′ arecylindrical in shape and define a continuous blood flow pathway 11′ fromopening 12 a′ to opening 14 a′.

[0105] The axes X-X and Y-Y are perpendicular in a preferred embodiment.Alternatively, the axes X-X, Y-Y could define an angle greater than 90°to provide a less turbulent blood flow from arm 12′ to arm 14′.

[0106] The conduit 10′ is positioned for the anchor arm 12′ to passthrough a preformed opening 50 in the heart wall 42 and extending fromthe lower surface 40 of the coronary artery 30 into the left ventricle44. The opening 12 a′ is in blood flow communication with the interiorof the left ventricle 44 so that blood may flow from the left ventricle44 directly into path 11′. The arm 14′ is coaxially aligned with thecoronary artery 30 and with the opening 14 a′ facing downstream (i.e.,in a direction facing away from obstruction 34).

[0107] Blood flow from opening 12 a′ passes through the pathway 11′ andis discharged through opening 14 a′ into the lumen 48 of the coronaryartery 30 downstream of the obstruction 34. The outer diameter of arm 14a′ is approximate to or slightly less than the diameter of the lumen 48.

[0108] The axial length of the anchor arm 12′ is preferably greater thanthe thickness of the heart wall 42 such that a length L protrudes beyondthe interior surface of the heart wall 42 into the left ventricle 44.Preferably, the length L of penetration into the left ventricle 44 isabout 1-3 millimeters in order to prevent tissue growth and occlusionsover the opening 12 a′.

[0109] In addition to directing blood flow downstream in the directionof arrow A, the arm 14′ holds the conduit 10′ within the coronary artery30 to prevent the conduit 10′ from otherwise migrating through thepreformed opening 50 and into the left ventricle 44. Additionally, anupper wall 14 b′ of arm 14′ defines a region 15′ against which bloodflow may impinge. Stated differently, in the absence of an arm 14′ orregion 15′, blood flow would pass through the anchor arm 12′ and impingedirectly against the upper wall 36 of the coronary artery 30. Highvelocity blood flow could damage the wall 36, as will be more fullydescribed, resulting in risk to the patient.

[0110] The region 15′ acts as a shield to protect the coronary artery 30from such blood flow and to redirect the blood flow axially out ofopening 14 a′ into the coronary artery 30. This is schematicallyillustrated in FIG. 23. For ease of illustration, the axis X-X of theanchor arm 12′ is shown at a non-orthogonal angle with respect to thedirection A of blood flow in the coronary artery 30 (axis X-X may beeither orthogonal or non-orthogonal to direction A). The vector B ofblood flow from the anchor arm 12′ has a vector component B′ parallel toblood flow A and a vector component B″ perpendicular to direction A. Theregion 15′ is positioned between the wall 36 and anchor arm 12′ toprevent the blood flow B with high vector component B″ from impingingupon wall 36. The blood flow deflected off region 15′ has a reducedvector component perpendicular to flow direction A and reducedlikelihood of damage to the coronary artery 30. The region 15′ may be aportion of an intracoronary arm 14′ or the arm 14′ may be eliminatedwith the region 15′ being an axially spaced extension from arm 12′ or aseparate shield surgically positioned within the coronary artery.

[0111] A portion 17′ of the anchor arm 12′ extends from the lowersurface 40 of the coronary artery 30 and through the lumen 48 to theupper surface 36 to block the cross-section of the coronary arteryupstream from opening 14 a′. The region 17′ acts as a barrier to impedeor prevent any dislodged portions of the obstruction 34 from passing theconduit 10′ and flowing downstream through the coronary artery 30.

[0112] The present invention maintains blood flow through the conduit10′ during both diastole and systole. Therefore, while the net bloodflow is in the direction of arrow A, during diastole, blood will flow ina direction opposite of that of arrow A.

[0113] The constantly open pathway 11′ results in a net flow in thedirection of arrow A which is extraordinarily high and sufficient toreduce or avoid patient symptoms otherwise associated with anobstruction 34. Specifically, certain aspects of the apparatus andmethod of the present invention have been preliminary tested in animalstudies. FIG. 22 schematically illustrates the tests as the placement ofa test conduit 10* in the coronary artery 30′ of a pig. For purposes ofthe tests, a stainless steel T-shaped conduit 10* is used having alignedopenings 14 a*, 16 a* positioned within the coronary artery 30′ and witha third opening 12 a* protruding 90° out of the coronary artery 30′. Theconduit 10* has a uniform interior diameter of 3 millimeters tocorrespond in sizing with a 3 millimeter lumen of coronary artery 30′.The third opening 12 a* is connected by a 3 millimeter conduit 13 to a 3millimeter rigid Teflon (PTFE) sleeve 13 a which was passed through theheart wall 42′ into the left ventricle 44′. The conduit 13 and sleeve 13a do not pass through the coronary artery 30′.

[0114] In the view of FIG. 22, the direction of net blood flow is shownby arrow A. A first closure device in the form of a suture loop 300surrounds the artery 30′ adjacent the upstream opening 14 a* of theconduit 10*. The loop 300 provides a means for closing the upstreamopening 14 a* by selectively constricting or opening the loop 300 toselectively open or block blood flow through the coronary artery 30′.The first loop 300 permits the test to simulate blockage of the coronaryartery 30′ upstream of the conduit 10*.

[0115] A flow meter 304 to measure volumetric flow of blood downstreamof the conduit 10* is placed adjacent downstream opening 16 a*. A secondclosure device 302 functioning the same as loop 300 is placed on conduit13 to selectively open or close blood flow through conduit 13.

[0116] When the second device 302 is closed and the first device 300 isopen, the conduit 10* simulates normal blood flow through a healthycoronary artery 30′ and the normal blood flow can be measured by theflow measuring device 304. By opening second device 302 and closing thefirst device 300, the test conduit 10* can simulate the placement of aconduit such as that in FIG. 21 with an obstruction located on theupstream side of the conduit. The flow meter 304 can then measure flowof blood through the conduit 10* during both diastole and systole.

[0117] The results of the tests indicate there is a substantial netforward blood flow (i.e., volumetric forward flow less volumetricretro-flow) with the second device 302 remaining open during bothdiastole and systole and with the first device 300 closed to simulate anobstruction. Specifically, in the tests, net blood flows in excess of 80percent of normal net forward blood flow were measured.

[0118] The amount of back flow through a conduit can be controlledwithout the need for providing a valve within the conduit. Convenientlyreferred to as flow “bias”, a volumetric forward flow greater than avolumetric rearward flow can be manipulated through a variety of meansincluding sizing of the interior diameter of the conduit, geometry ofthe conduit (e.g., taper, cross-sectional geometry and angle) and, aswill be more fully discussed, structure to restrict rear flow relevantto forward flow.

[0119] The sizing of the interior diameter of the flow pathway 11′ canbe selected to minimize back flow. As will be more further discussed,the net flow increases with a reduction in the diameter as suggested bysimulation modeling of flow through a conduit. One method in which shearrate and flow bias can be controlled is by providing a tapered diameterfor a narrower diameter at opening 14 a′ than at opening 12 a′. Theselection of the conduit geometry (e.g., an angled anchor arm as shownin FIG. 23 or a tapered geometry as will be discussed with reference toFIG. 20) can be selected to modify the degree to which the conduit isbiased to net forward flow (i.e., the conduit offers less resistance toforward flow than to retro-flow) without stopping or blockingretro-flow.

[0120] The substantial net blood flow measured in animal testing throughthe invention is extraordinarily high when compared to minimumacceptable levels of net blood flow following traditional bypasstechniques (i.e., about 25 percent of normal net blood flow). Further,the results are counter-intuitive and contradictory to the priorteachings of the art of U.S. Pat. Nos. 5,429,144; 5,287,861 and5,409,919 and the afore-mentioned Munro et al. article. In addition, thepresent invention provides a conduit with a shielding area to preventdamaging impingement of blood flow directly onto the coronary arterywall as well as providing a blocking area to prevent the migration ofdebris from an obstruction to a location downstream of the conduit.

[0121] Having provided a summarized version of the present inventionwith reference to the schematic drawings of FIGS. 21 and 22, a moredetailed description of the present invention as well as a detaileddescription of alternative embodiments and alternative surgicalprocedures will now be provided.

[0122] B. Embodiments with an Open Chest Approach

[0123] 1. The Apparatus of the Present Invention for Use in the OpenChest Approach

[0124] As will be more fully described, the present invention places anapparatus for defining a blood flow conduit directly from a chamber of aheart to a coronary artery downstream of an occluded site. Beforedescribing the surgical methods for placing such an apparatus, anapparatus of the present invention will be described. The apparatus ofthe present invention can be a variety of shapes or sizes, and is notmeant to be limited as to size, shape, construction, material, or in anyother way by the following examples in which a preferred embodiment isillustrated.

[0125] a. T-Shaped Device

[0126] With initial reference to FIGS. 2A, 2B, 2C, 2D and 2E, relatedembodiments of an apparatus according to the present invention are shownas a rigid T-shaped conduit 10 (a preferred L-shaped conduit 10′ havingalready been summarized and to be later described in detail). Theconduit 10 is hollow and includes two axially-aligned intracoronary arms14, 16 terminating at open ends 14 a, 16 a. An anchor arm 12 (having anopen end 12 a) extends perpendicularly to arms 14, 16. The entireconduit 10 is hollow to define a blood flow conduit 11 providing bloodflow communication between open ends 12 a, 14 a and 16 a.

[0127] As will be more fully discussed, arms 14 and 16 are adapted to beplaced and retained within a lumen of a coronary artery on a downstreamside of an occlusion with open ends 14 a, 16 a in blood flowcommunication with the lumen. The anchor arm 12 is adapted to extendthrough and be retained in a heart wall (e.g., wall of the leftventricle) with the open end 12 a in blood flow communication with bloodwithin the chamber. When so placed, the conduit 10 defines asurgically-placed conduit establishing direct blood flow from the heartchamber to the artery. By “direct” it is meant that the blood flow doesnot pass through the aorta as occurs in traditional bypass procedures.The conduit 10 is sufficiently rigid such that it defines an open bloodflow path during both diastole and systole.

[0128] b. Optional Forward Flow Bias

[0129] While unobstructed back flow is preferred, partially restrictedback flow can be provided. As will be more fully described, back flowcan be controlled by the geometry of the conduit. The followingdescribes a presently less preferred alternative embodiment forcontrolling back flow.

[0130]FIG. 2B illustrates use of an optional bi-directional flowregulator 22 within the conduit 10 and positioned in anchor arm 12. Thebi-directional flow regulator 22 permits unimpeded flow in the directionof arrow A (i.e., from open end 12 a to open ends 14 a, 16 a) whilepermitting a reduced (but not blocked) reverse flow.

[0131]FIG. 2C illustrates the use of a first bi-directional flowregulator 22 as well as a second bi-directional flow regulator 26 in arm16 near the open end 16 a of the apparatus. The second bi-directionalflow regulator 26 permits unimpeded blood flow in the direction of arrowB. The second bi-directional flow regulator 26 is used to permit areduced (but not zero) back flow of blood in an upstream directionwithin the coronary artery. For example, the coronary artery may not becompletely obstructed and may have a reduced flow past an obstruction.The use of the T-conduit 10 with axially aligned arms 14, 16 takesadvantage of such reduced flow and supplements such flow with bloodthrough anchor arm 12. As will be described, the conduit 10 is placedwith the arms 14, 16 in the lumen of the artery with opening 16 apositioned on the upstream side (i, nearest to, but still downstream of,the obstruction).

[0132] As indicated above, the flow regulator 22 is a bi-directionalflow regulator. By this it is meant that the flow regulator 22 does notblock flow of blood in any direction. Instead, the flow regulator 22permits a first or maximum flow rate in one direction and a second orreduced flow rate in a second direction. The flow regulator isschematically illustrated in FIGS. 18A through 19C. In each of theseembodiments, the arrow A indicates the direction of blood flow from theleft ventricle to the coronary artery.

[0133]FIGS. 18A through 18C illustrate one embodiment of abi-directional flow regulator 22. FIGS. 19A through 19C illustrate analternative embodiment of a bi-directional flow regulator 22. Theregulator 22 of FIGS. 18A through 18C shows a butterfly valve 222mounted in the anchor arm 12 of a rigid conduit 10. Valve 222 may bepivoted (in response to blood flow in the direction of arrow A) betweena position with the plate 222 generally parallel to the walls 12 of theconduit 10 as illustrated in FIG. 18A. The plate 222 can be rotated (inresponse to blood flow reverse to arrow A) to a position angled relativeto the walls 12 of the conduit 10 as illustrated in FIG. 18B. FIG. 18Amay be conveniently referred to as a full flow position. FIG. 18B may beconveniently referred to as a reduced flow position. FIG. 18C is across-section of the conduit 10 when the plate 222 is in the reducedflow position.

[0134] The plate 222 is sized relative to the conduit 10 such that thecross-sectional area of the conduit 10 which remains open is sufficientto permit about 20% of the blood flow (measured volumetrically) to flowback through the conduit 10 in a direction opposite to that of arrow Aduring diastole. As a result, during systole, blood flow from the heartto the coronary artery urges the plate 222 to the full flow position ofFIG. 18A such blood may flow unobstructed through the device to thecoronary artery. During systole, the blood (due to pressuredifferentials between the coronary artery and the left ventricle) willflow in a direction opposite of that of arrow A causing the plate 222 torotate to the position of FIG. 18B and 18C. However, even in the reducedflow position, the plate 222 is prevented from moving to a full closedposition such that flow through the device is never blocked and insteadmay proceed with a back flow of about 20% (volumetrically measured) ofthe normal flow in the direction of A.

[0135]FIGS. 19A through 19C show an alternative design of the conduit 10with the flow regulator 22 a in the form of three leafs 222 a, 222 b,222 c which, in response to blood flow from the left ventricle to thecoronary artery, open to a full open position shown in FIG. 19B and moveto a restricted flow position in FIGS. 19A and 19C in response to backflow. The leaves 222 a, 222 b, 222 c are provided with openings 223 topermit flow through the leaves 222 a, 222 b, 222 c at all times.

[0136] It is believed that providing a back flow of about 20% (20% beinga non-limiting example of a presently anticipated desired back flowrate) of the volumetric anterograde flow is necessary. This is essentialbecause it allows the channel of the conduit 10 and the mechanicalelements of the flow regulator 22 to be washed by the retrograde flow.This ensures that no areas of stagnant flow occur. Areas of stagnation,if allowed, could result in clot formation which could result in thrombioccluding the conduit or breaking loose. Thrombi could be carrieddownstream into the coronary arteries to cause one or more areas ofcardiac muscle ischemia (i.e., a myocardial infarction) which could befatal. Back flow necessary to wash the components can be achievedthrough either a conduit 10 which has a constant opening through bothsystole and diastole (i.e., conduit 10 of FIG. 2A without the use of abi-directional flow regulator 22) or with a device coupled with abi-directional flow regulator 22 (FIGS. 2B-2C) which permits a 20% flowrate back flow during diastole.

[0137] c. L-Shaped Device

[0138] Preferably, an L-shaped conduit 10′ (FIGS. 1A, 1B, 1C) is used tocompletely bypass the coronary obstruction. An L-shaped conduit 10′ hasan anchor arm 12′ with an open end 12 a′. Unlike conduit 10, conduit 10′has only one intracoronary arm 14′ perpendicular to arm 12′. Arm 14′ hasan open end 14 a′ and conduit 10′ is hollow to define a continuous fluidpathway 11′ from end 12 a′ to end 14 a′. In application, arm 14′ isplaced within the lumen of an artery. End 14 a′ faces downstream from anobstruction. Arm 12′ is placed through the heart wall with end 12 a′ influid communication with blood within the heart chamber. As illustratedin FIG. 1B, the anchor arm 12′ can include a bi-directional flowregulator 22′ similar to bi-directional flow regulator 22 of conduit 10.

[0139] d. Optional Flexible Anchor Arm

[0140] Conduit 10, 10′ may be rigid, or have varying flexibilities.Regardless of such flexibility, the conduit 10, 10′ should besufficiently rigid for pathway 11, 11′ to remain open during bothdiastole and systole. FIGS. 3A, 3B and 3C demonstrate one embodimentwhere the anchor arm (i.e., elements 12, 12′ of FIGS. 1A and 2A) iscomprised of a number of rings 17 surrounded by a membrane 18. In FIGS.3A-3C, only anchor arm 12 is shown. It will be appreciated that anchorarm 12′ may be identically constructed.

[0141] In the embodiment of FIGS. 3A-3C, the rings 17 can be constructedof Teflon, and the surrounding membrane 18 can be constructed of adouble-walled Dacron sheath into which the rigid supporting rings 17 aresewn. In this embodiment, the rings 17 provide structural strength. Thestructural strength maintains an open lumen or conduit 11 leading intothe coronary artery by preventing the conduit 11 from collapsing byreason of contraction of the heart muscle surrounding the anchor arm 12.The series of rings 17 provide a degree of flexibility which allows achannel formed through the heart chamber muscular wall (receiving anchorarm 12) to be angled or curved. In addition, the flexibility of thesurrounding sheath 18 in concert with the rigid rings 17 will allow theanchor arm 12 to expand, FIG. 3B, and contract, FIG. 3C, with thecontractions and relaxations of the surrounding cardiac musculature.

[0142] It should be noted that, because of the semi-rigid nature of theanchor arm 12 constructed in this manner, a method of attaching that endof the anchor arm in contact with the inner surface of a chamber of aheart can be useful. In the example illustrated, this attachingmechanism 19 is a rigid flange 12 a. It will be appreciated that othermechanisms of attachment, such as suturing, biologically gluing, etc.are alternative options.

[0143] e. Optional Blood Reservoir

[0144] The apparatus of the present invention (as thus described)provides a path 11 through which blood flows from a chamber of a heartand into a coronary artery. Additionally, such a device can store bloodunder pressure for a period of time prior to its introduction into acoronary artery. As depicted in the embodiments of FIGS. 1C and 2D, thisaspect of the conduit 10, 10′ of the present invention is referred to asa capacitance pressure reservoir (CPR) 24, 24′.

[0145] Blood flow through the normal coronary artery is cyclical. Bloodflow is increased during diastole (when the heart muscle is in arelaxing state), and decreases or reverses during systole (when theheart muscle is in a contracting state). See, e.g., F. Kajiya et al.,Velocity Profiles and Phasic Flow Patterns in the Non-Stenotic HumanLeft Anterior Descending Coronary Artery during Cardiac Surgery, 27Cardiovascular Res. 845-50 (1993).

[0146] The pressure gradient across the lumens 12 a, 12 a′, 14 a′, 16 aof the apparatus 10, 10′ of the present invention will vary over thecardiac cycle. For example, during systole, the contraction of the heartmuscles will generate high relative pressures within the left ventricle.

[0147] The pressures within the coronary arterioles and capillariesdistal to the bypass site can also be high during this time, due to theexternal compression of the contracting cardiac musculature surroundingthese vessels. This is particularly true for the vessels of themicrocirculation deep within the heart which serve the endocardium.

[0148] The optional CPR 24, 24′ stores the pressurized blood duringsystole for delivery to the heart muscles via the coronary circulationduring diastole when pressures are reduced. In essence, the CPR 24, 24′serves a function similar to the elastic connective tissue of thethick-walled aorta. The necessary function of the CPR 24, 24′ is tostore blood under higher pressure, and to later provide that storedblood to the microcirculation when the external pressures on thatmicrocirculation are reduced.

[0149] As depicted in FIG. 1C and 2D the bi-directional flow regulators22, 22′ provide full blood flow in the direction of A, which is from achamber of a heart into the conduit 10, 10′ via the lumen 11, 11′. Thepressure on the blood within the chamber of a heart will be greatestwhen the surrounding cardiac musculature is in the contracting phase ofthe cardiac cycle. Because it is during this phase of the cardiac cyclethat the external pressure on the coronary artery microcirculation isalso highest, blood flow through the lumen 11, 11′ of the conduit 10,10′ could be limited. To counteract this tendency, the conduit 10, 10′is equipped with a reservoir 24, 24′ which stores this pressurized bloodflowing from a chamber of the heart during the cardiac contraction.

[0150] The reservoir, or CPR 24, 24′ is schematically illustrated inFIGS. 1C, 2D. It can be appreciated that the conduit 10, 10′ is providedwith a fluid passage 28, 28′ in communication with pathway 11, 11′. Thepassage 28, 28′ communicates with an expandable volume (or storagechamber) 27, 27′ defined by a movable wall 31, 31′ contained within afixed housing 33, 33′. Springs 29, 29′ between wall 31, 31′ and housing33, 33′ urge the wall 31, 31′ to move to reduce the size of volume 27,27′. The springs 29, 29′ are pre-loaded to exert a force on wall 31, 31′less than a force exerted by blood within volume 27, 27′ during thecontraction phase of the cardiac cycle, but greater than the forceexerted by blood within volume 27, 27′ during the relaxation phase ofthe cardiac cycle.

[0151] The conduit 10, 10′ is constructed in a manner which allows bloodto flow into the storage chamber 27, 27′ of the conduit 10, 10′ throughthe lumen 11, 11′ of arm 28, 28′ of the conduit when the cardiacmusculature is contracting. When blood is flowing into the storagechamber 27, 27′, the kinetic energy of the flowing blood is converted topotential energy, and stored in 29, 29′. During the relaxation phase ofthe cardiac musculature, the potential energy stored in 29, 29′ of theCPR 24, 24′ is then re-converted to kinetic energy in the form of bloodflow out of the storage chamber 27,27′ of the conduit 10, 10′ via thelumen 11, 11′ of arm 28, 28′ of the conduit.

[0152] While the CPR 24, 24′ is illustrated with a movable wall 31, 31′and springs 29, 29′ to define a variable volume, other designs can beused. For example, the CPR 24, 24′ can be a balloon-like structure. Asit fills with blood, the pressure on that blood increases through thestretching of an elastic component of a balloon. In another embodiment,the CPR, 24, 24′, can be a hollow bag, made of a material which iselastic, but impermeable to liquids, and pliable similar to a plasticbag. When the heart contracts, blood is forced through lumen 11, 11′ ofarm 28, 28′ of the apparatus 10, 10′ of the invention into thecollection bag.

[0153] The incorporation of bi-directional flow regulators 22, 22′within the anchoring arm 12, 12′ of the conduit 10, 10′ provide most(about 80%) of the flow of blood out of the device during diastole tothe coronary artery via the lumen 11′ 11′ of arms 14 a, 14 a′, 16 a ofthe device, of the conduit 10, 10′. Similarly, the incorporation of thebi-directional flow regulator 26 within the intracoronary arm 16 of theT-shaped conduit 10, when employed with the bi-directional flowregulator 22 within the anchor arm 20 of the conduit 10, would providemost of the flow of blood out of the device during diastole to theportion of the coronary artery distal to the bypass site via thedownstream lumen 11 of arm 14 a.

[0154] f. Sizing of the Conduit

[0155] The inner and outer cross-sectional diameters of a coronaryartery decreases with the distance from the arterial origin. Eventually,the artery branches into a number of arterioles, which feed thecapillary bed of the coronary arterial microcirculation.

[0156] The typical diameter of a lumen of a coronary artery is, ingeneral, species specific; increasing with heart size. In humans, thislumen diameter is dependent upon which artery is being evaluated, butusually ranges from 1.0 to 4 mm in diameter, and decreases with distancefrom the aortic origin. In the preferred embodiment, the cross-sectionalouter diameter of the intracoronary arms 14, 14′, 16 of the device ofthe present invention should effectively approximate the diameter of thelumen of the coronary artery being bypassed, at the bypass site. Thisallows the complete re-approximation of the previously openedsuperficial wall of the coronary artery during surgical closure, withouthigh suture or staple tension resulting. In the most preferredembodiment, the outer diameter of the intracoronary arms 14, 14′, 16 ofthe conduit 10, 10′ of the present invention is equal to the diameter ofthe lumen of the coronary artery which is being bypassed, at the bypasslocation. When a CPR is placed, the artery wall may need to be expandedby the addition of a patch, such as Dacron, well known in the art.

[0157] Also, due to smooth muscle relaxation and secondary vasculardilation, the cross-sectional diameter of a lumen of a coronary arterywill increase with the oxygen demand of cardiac muscle during times ofstress. The cross-sectional inner diameter of the intracoronary arms 14,14′, 16 of the conduit 10, 10′ of the present invention shouldeffectively approximate that diameter necessary to provide adequateblood flow through the downstream lumen of the conduit to effectivelyoxygenate the cardiac musculature normally supplied by themicrocirculation of the coronary artery. In the preferred embodiment,the cross-sectional inner diameter of the intracoronary arms 14, 14′, 16of the conduit 10, 10′ of the present invention should effectivelyapproximate that diameter necessary to provide adequate blood flowthrough the lumen of the device to effectively oxygenate the cardiacmusculature normally supplied by the microcirculation of the coronaryartery during both times of cardiovascular resting and stress.

[0158] If necessary, an initial approximation of the requiredcross-sectional outer diameter of the intracoronary arms 14, 14′, 16 ofthe conduit 10, 10′ of the present invention can be gained by standardradiographic techniques. Also, in the alternative embodiment apparatuswhen a bi-directional flow regulator 22, 22′ is desired, the operatingpressure of the bi-directional flow regulator 22, 22′ (i.e., thepressure at which the flow regulator moves from a reduced back-flow to afull forward flow position) can be determined by the dynamicmeasurements of coronary artery pressure, blood flow, and heart chamberpressures through selective catheterization with standard techniques.See Minoru Hongo et al., 127(3) Am. Heart J. 545-51 (March 1994).

[0159] During the coronary artery bypass procedure, the most appropriatesizing of the intracoronary arms 14, 14′, 16 of the conduit 10, 10′ ofthe present invention can be re-assessed. This can be accomplished byprobing the distal and, if needed, the proximal aspects of the coronaryartery at the chosen bypass site with blunt instruments of known outerdiameters. Such sizing by probes is well-known in the literature. Tofacilitate the effective matching of the external diameter of theintracoronary arms 14, 14′, 16 of the conduit 10, 10′ of the presentinvention to the lumen 34 of the coronary artery to be bypassed, anassortment of conduits of the present invention of various diameters canbe available for the surgeon to select from.

[0160] The anchor arm 12, 12′ is sized to maximize net blood flow fromthe left ventricle to the coronary artery. Through simulation testing, acounter-intuitive indication is that maximizing the diameter of anchorarm 12, 12′ is not desirable. For example, such simulation assumingdiameters of 3.00 mm, 2.25 mm and 1.50 mm for an unrestricted fistula(i.e., without a flow regulator 22) suggests that the smaller diameterof 1.50 mm most closely approximates normal coronary blood flow andminimizes back flow thus maximizing net forward flow.

[0161] It is desirable that the anchor arm 12, 12′ protrudes into theheart chamber such that end 12 a is spaced from the heart wall. Thisprevents tissue growth over end 12 a.

[0162] Finally, it will be noted that the anchor arm 12 defines alongitudinal axis (e.g., axis X-X in FIG. 18A). The region 15 of arms14, 14 intersects axis X-X. The region 15 acts as a deflection surfaceto prevent high velocity blood flow from arm 12 impinging directly uponthe coronary artery wall. Instead, the high velocity blood flow impingesupon region 15 and is directed axially into the coronary artery. As aresult, the coronary artery wall covered by region 15 is protected fromdamage which would otherwise be caused by the high velocity blood flowand the blood components are transitioned to axial flow with a minimumof cell damaging shear.

[0163]FIG. 20 shows a still further embodiment 10″ where the anchor arm12″ has a longitudinal axis X′-X′ at a non-orthogonal angle relative tothe axis Y′-Y′ of the coronary arms 14″, 16″. Further, the anchor arm12″ has a taper. In other words, the arm 12″ is widest at opening 12 a″.The taper and angle act to reduce blood flow velocity and to restrictback flow (arrows B) while facilitating forward flow (arrow A′). Also,the blood in the forward flow A′ impacts against the deflection region15″ at an angle to reduce impact of blood cells.

[0164] 2. The Method of the Present Invention Using the Open ChestApproach

[0165] a. General

[0166] The method of the present invention is suitable for performing avariety of surgical cardiac procedures. The procedures may be performedutilizing an open-chest approach, or through minimally invasiveapproaches by the creation of access means into the chest, or throughpercutaneous access utilizing intracoronary and intraventricularcatheterization. Dependent on the invasiveness of the approach utilized,the heart can be allowed to pulse normally, be slowed by varyingamounts, or stopped completely. A significant period of complete heartstoppage can necessitate the use of supportive cardiopulmonary bypass.

[0167] The method of the present invention for performing a coronaryartery bypass procedure will now be described in detail. The patient whois to undergo the procedure can be prepared in a conventional manner forcardiac bypass surgery. The patient preparation, anesthesia utilized,and access route to the coronary circulation, will vary depending uponthe invasiveness of the specific procedure chosen.

[0168] b. Preparation for the Procedure

[0169] i. General Preparations

[0170] Standard techniques of general preparation for open-chest surgeryin which cardiopulmonary bypass is utilized have been widely reported.See, e.g. Ludwig K. Von Segesser, Arterial Grafting For MyocardialRevascularization (1990). In one embodiment of the methods of theinvention where an open-chest procedure and cardiopulmonary bypass isutilized, the patient can be prepared for surgery as outlined by VonSegesser.

[0171] General preparations for open-chest surgery in whichcardiopulmonary bypass is not utilized have been published by Buffolo etal., 61 Ann. Thorac. Surg. 63-66(1996). In one embodiment of the methodsof the invention where an open-chest procedure without cardiopulmonarybypass is utilized, the patient can be prepared for surgery as outlinedby Buffolo.

[0172] General preparations for closed-chest surgery, to be performedusing thoracoscopy and where cardiopulmonary bypass is utilized, havebeen outlined by Sterman et al., U.S. Pat. No. 5,452,733 (1995). In oneembodiment of the methods of the invention where a closed-chestprocedure and cardiopulmonary bypass is utilized, the patient can beprepared for surgery as outlined by Sterman.

[0173] General preparations for closed-chest surgery to be performedusing thoracoscopy, but where cardiopulmonary bypass is not utilized,have been published by Acuff et al., 61 Ann. Thorac. Surg. 135-37(1996). In one embodiment of the methods of the invention where aclosed-chest procedure without cardiopulmonary bypass is utilized, thepatient can be prepared for surgery as outlined by Acuff.

[0174] General preparations for percutaneous coronary artery bypassgrafting utilizing intracoronary and intraventricular catheterizationand without cardiopulmonary bypass have been described by Wilk in hisafore-mentioned U.S. patents. Preparations can include the sterilescrubbing and draping of at least one groin to permit access to afemoral artery for catheterization of the coronary vasculature and thesterile scrubbing and draping of the right superior anterior chest wallto permit access to the innominate artery for catheterization of theleft ventricle. Further suggested preparations can include thoseoutlined by Sterman and Acuff for thoracoscopic surgery with and withoutcardiopulmonary bypass, respectively.

[0175] ii. Anesthesia Prior to and During the Procedure

[0176] Most often, the patient will be placed under general anesthesiaprior to the procedure. In one embodiment, standard cardiac operativeanesthetic techniques, such as premedication with diazepam, inductionwith propofol and sufentanil, and maintenance with desflurane can beemployed. On occasion, less than general anesthesia can be utilized.Less than general anesthesia is well known in the literature. When theinvasiveness of the procedure is minimal, such as when the procedure isto be carried out via intracoronary and intraventricularcatheterization, or when the risks of general anesthesia to theindividual patient outweighs the risks of less than general anesthesiawith regard to the particular procedure planned, less than generalanesthesia can be induced. Selective ventilation of the lungs can beachieved through the placement of a double-lumen endobronchial tubewhich independently provides for the intubation of the left and rightmain stem bronchi. An intraesophageal probe can be placed to facilitatecardiac monitoring and the synchronization of power to the laser, whendeemed useful.

[0177] iii. Access to the Heart and Coronary Vasculature for theProcedure

[0178] Following preparation, access to the patient's coronary arterialvasculature can be attained through a variety of techniques, dependentupon the route of access chosen.

[0179] Von Segesser has reported a method of access to the coronaryarterial vasculature when utilizing an open-chest approach andcardiopulmonary bypass. In one embodiment, utilizing an open-chestapproach with cardiopulmonary bypass, access to the coronary vasculaturecan be obtained as reported by Von Segesser.

[0180] Buffolo et al. has reported an open-chest approach to thecoronary arterial vasculature when performed without cardiopulmonarybypass. See Buffolo et al., 61 Ann. Thorac. Surg. 63-66 (1996). In oneembodiment utilizing an open-chest approach without cardiopulmonarybypass, access to the coronary vasculature can be obtained as reportedby Buffolo.

[0181] Sterman et al. has reported a method of access to the coronaryarterial vasculature when a closed-chest approach with cardiopulmonarybypass is utilized. See Sterman et al., U.S. Pat. No. 5,452,733 (1995).Sterman positions a plurality of access trocar sheaths along thepatient's left and right anterolateral chest wall. These trocar sheathsprovide access to the coronary vasculature, and allow the temporaryrepositioning of the heart to facilitate the performance of theprocedure. The repositioning is accomplished utilizing grasping toolsintroduced through the appropriate trocar sheaths. Visualization duringthis procedure can be either indirectly via thoracoscopy, or directlyvia a ‘window’ placed in the left middle anterior chest wall by thesurgical removal of the fourth rib. Access to the bypass site cantherefore be obtained by following the techniques outlined by Sterman.The instruments to be used in the procedure can also be similar to thosedescribed by Sterman.

[0182] Acuff et al. has described a method of access to the coronaryarterial vasculature when a closed-chest approach withoutcardiopulmonary bypass is utilized. See Acuff et al., 61 Ann. Thorac.Surg. 135-37 (1996). Similar to the techniques of Sterman, Acuffpositions a plurality of access trocar sheaths along the patient's leftand right anterolateral chest wall. Also similar to Sterman, Acuffsurgically establishes an access space, or window in the left anteriorchest wall through the removal of the left fourth rib cartilage. Thetrocar sheaths, in concert with this window, allow the temporaryrepositioning of the heart, and access to the coronary arterialvasculature. Visualization during this procedure can be eitherindirectly via thoracoscopy, or directly via the window. Access to thebypass site can therefore be obtained by following the techniquesoutlined by Acuff. The instruments to be used in the procedure can alsobe similar to those described by Acuff.

[0183] Access to a chamber of a heart and a coronary artery when thebypass is performed through the percutaneous approach of intracoronaryand intraventricular catheterization can be obtained as follows. Accessto a coronary artery can be obtained by the introduction of a catheterinto the left or right femoral artery through an arterial cut downprocedure. The catheter can then be fed retrograde past the descendingaorta, through the ascending aorta, and into the coronary artery bystandard catheterization techniques. In a preferred embodiment, accessto a chamber of the left side of a heart can be obtained by theintroduction of a catheter into the innominate artery, also through anarterial cut down procedure. In the most preferred embodiment, access tothe left ventricle is obtained by the introduction of a catheter intothe innominate artery and the advancement of this catheter into the leftventricle. In this embodiment, the catheter is advanced through theascending aorta, past the aortic valve. and into the left ventricle.Techniques by which the left ventricle is catheterized are well known inthe literature. 3. Open Chest Approach

[0184] In the coronary artery bypass graft procedures of the presentinvention, a chamber of a heart provides blood to a coronary artery. Themethod of the present invention can accomplish this by establishing oneor more channels through the wall of a chamber of a heart which leaddirectly from a chamber of a heart into a coronary artery at a sitedistal to the narrowing or blockage. The methods of the invention invarious embodiments can achieve the establishment of such a channel orchannels through a variety of techniques.

[0185] Referring now to FIGS. 4, 5, 6, 7, 8, and 9, an exemplaryopen-chest procedure, which may or may not include cardiopulmonarybypass, by which a coronary artery bypass procedure may be accomplishedwill be described. The open-chest approach affords maximal access to,and visualization of, the coronary vasculature; although at the expenseof injury to normal tissue.

[0186] Through the methods of the present invention, the conduit 10, 10′of the present invention, which provides blood from a chamber of a heart43 directly into a coronary artery 30, is placed. To illustrate theinvention, only placement of conduit 10′ is discussed. It will beappreciated that conduit 10 can be similarly placed. In addition,examples will be limited to the embodiment of the conduit of theinvention as illustrated in FIG. 1A.

[0187] Preparation for the procedure, and anesthesia prior to and duringthe procedure, is outlined above.

[0188] First, the chest cavity is entered, and pericardium 52 incisedanteriorly, to expose a coronary artery 30 (having an obstruction 34) tobe bypassed. This is illustrated in FIG. 4.

[0189] Second, cardiopulmonary bypass may be initiated by a variety ofstandard techniques as outlined by George Silvay et al., CardiopulmonaryBypass for Adult patients: A Survey of Equipment and Techniques, 9(4) J.Cardiothorac. Vasc. Anesth. 420-24 (August 1995).

[0190] Third, if bypassed, the heart is slowed and/or stopped by avariety of standard techniques. One standard technique is toelectrically induce ventricular fibrillation. Another standard techniqueis warm or cold blood cardioplegia, delivered antegrade or retrograde,and intermittent or continuous, as outlined by Gerald D. Buckberg,Update on Current Techniques of Myocardial Protection, 60 Ann. Thorac.Surg. 805-14 (1995).

[0191] Fourth, the heart is inspected and coronary arteries identified.The narrowed or occluded coronary artery 30 can be visually identified,and an appropriate site distal or downstream from the occlusion 34chosen.

[0192] Fifth, blood flow through the target coronary artery 30 is haltedby standard techniques. For example, standard techniques includeclamping the aorta above the coronary ostia with an arterial clamp.Alternatively, in the beating heart procedure, the flow of blood withinthe coronary artery 30 can be halted by forming a loop around the artery30 with suture either proximally, or both proximally and distally, andapplying appropriate tension on the suture or sutures, or tying thesuture or sutures.

[0193] Sixth, depending on the degree of exposure deemed necessary, theepicardium overlying the coronary artery at the selected bypass site isincised. This exposure can facilitate locating the lumen of the coronaryartery 30 via palpation.

[0194] Seventh, as shown in FIG. 5, the superficial wall 36 of thecoronary artery 30 is longitudinally incised by standard techniques,such as incision with a scalpel, electrosurgical cutting device, orsimilar tool; taking care not to damage the deep wall of the artery.This initial incision can be lengthened, if necessary, to accommodatethe intracoronary arms 14′ using standard tools such as fine angledscissors.

[0195] Eighth, a channel 50 is initiated into the deep coronary arterialwall 40 and through the musculature 42 of a chamber of a heart. In thepreferred embodiment, the chamber of a heart is the left ventricularchamber of the heart. The channel 50 can be initiated by standardtechniques such as awl punching, incising, use of a laser, or the like.The channel 50 is then extended into the chamber of a heart, in thiscase the left ventricle 44, by standard techniques (such as punchingwith a trocar 46, incising with a scalpel blade, electrosurgical cuttingwith an electrosurgical cutting tool, laser or radio frequency ablation,blunt dissection, etc.).

[0196] Ninth, once a channel extending through the entire thickness of awall 42 of a chamber of a heart is formed, it can be systematicallysized by the passage of standard probes.

[0197] Tenth, through palpation, inspection, and probing of the distaland proximal coronary artery lumen 48, a conduit 10′ of appropriatedimensions is selected, as outlined above.

[0198] Eleventh, as illustrated in FIGS. 7 and 8, the anchor arm 12′ isinserted into the formed channel 50. The intracoronary arm 14′ is thenseated within the lumen 48 of the coronary artery 30.

[0199] Twelfth, as shown in FIG. 9, the longitudinal incision 38previously incised in the anterior wall 36 of the coronary artery 30 issurgically re-approximated. The re-approximation can be performed by anumber of conventional techniques, including suturing 52, laser welding,microstapling, and the like.

[0200] Thirteenth, the clamps or sutures closing off blood flow to thecoronary artery are released.

[0201] Fourteenth, contractions of the heart, if previously stopped, arereinitiated by standard electrostimulation or the reversal ofcardioplegia and the patient is slowly weaned from cardiopulmonarybypass by standard techniques.

[0202] Fifteenth, the pericardium, sternum, and overlying skin of thechest is re-approximated and surgically closed by standard, conventionaltechniques.

[0203] Sixteenth, anesthesia is reversed and the patient revived bystandard techniques.

[0204] D. Embodiments for a Closed Chest Approach

[0205] 1. The Apparatus of the Present Invention for Use in the ClosedChest Approach

[0206] A closed chest approach according to the method of the presentinvention may use the conduit 10, 10′ as described above. Such aprocedure will now be described. Following this description, a closedchest approach using alternative embodiments of the apparatus of theinvention will be described.

[0207] 2. The Method of the Present Invention Using the Closed ChestApproach

[0208] An exemplary closed-chest procedure, without cardiopulmonarybypass, by which a coronary artery bypass may be accomplished will nowbe described. The closed-chest approach is less invasive than theopen-chest approach, although providing the surgeon with somewhat poorervisualization and limited direct access to both the chambers of theheart and coronary artery bypass site.

[0209] Preparation for the procedure, and anesthesia prior to and duringthe procedure, is outlined above.

[0210] First, a plurality of access trocar sheaths is positionedanterior and laterally along the left and right chest walls as outlinedby Acuff et al.

[0211] Second, a space in the left low anterior chest wall may be formedby removal of the fourth rib cartilage, as outlined by Acuff et al. Inthis embodiment, the heart and coronary artery can be both directlyviewed via this space or window, as well as indirectly visualized via athoracoscope.

[0212] Third, a standard pericardiotomy is performed using a scalpel orelectrosurgical cutting tool introduced through the left lateral chesttrocar sheaths while viewing under thoroacoscopy. The pericardium can beexcised and either spread open, or removed from the thoracic cavity asoutlined by Acuff et al.

[0213] Fourth, if necessary, the heart can be rotated within themediastinum. Direct access and visualization through the formed chestwall space can require rotation of the heart. Rotation of the heart canbe accomplished by the grasping of the heart by tools inserted throughaccess trocar sheaths located along the left and right chest wall asdescribed by Sterman et al. Alternatively, traction on sutures placed inthe pericardium can distract the heart allowing appropriate directvisualization of the area to be bypassed as described by Acuff et al. Inanother alternative procedure, the heart can be accessed from thepatient's back with an endoscope for implantation of the stent in theposterior vascular beds which are not currently accessible by minimallyinvasive techniques.

[0214] Fifth, once the coronary artery to be bypassed is identified andwell-visualized; snare sutures of 5-0 polypropylene are placed at leastproximally to the target area as described by Acuff et al.

[0215] Sixth, the heart rate can be pharmacologically slowed toapproximately 40 beats/minute to minimize motion within the operativefield as described by Acuff et. al. Nitroglycerin and heparin can alsobe administered to reduce cardiac ischemia and prevent clottingrespectively as outlined by Acuff et al.

[0216] Because cardiopulmonary bypass is omitted in this embodiment,intermittent coronary artery occlusion to induce ischemicpreconditioning, as well as transesophageal echocardiography to reviewcardiac wall motion changes, can be utilized as described by Acuff etal. The epicardium can be incised over the area selected for bypass andthe anterior surface of the artery cleared under direct visualizationthrough the space or window, or via remote instruments inserted throughthe trocar sheaths under thoracoscopic guidance.

[0217] Seventh, in situations where the coronary artery can be directlyviewed, the lumen 48 of the coronary artery is identified by palpation.Either under direct visualization, or under thoracoscopic guidance andusing instruments manipulated through the trocar sheaths, thesuperficial wall 36 of the coronary artery is then longitudinallyopened. As above, care is taken to leave the deep wall 40 of the arteryundamaged. The incision 38 can be enlarged, as necessary, to accommodatethe intracoronary arms 14, 14′, 16 of the conduit 10, 10′ using fineangled scissors. This enlargement can be performed with standardsurgical scissors under direct viewing through the window, or via othersurgical instruments remotely manipulated following their insertionthrough the trocar sheaths.

[0218] Eighth, a channel 50 through the heart wall is initiated byincising or laser ablating into the deep wall 40 of the coronary artery.This also can be performed by standard surgical tools under directviewing, or by the remote manipulation of specialized instrumentsintroduced through the trocar sheaths and viewed thoracoscopically. Thechannel 50 is then extended through the deep coronary arterial wall 40,through underlying cardiac musculature 42, and into the underlyingchamber of the heart 44 by incising with a scalpel or electrosurgicalcutting blade, laser ablation, blunt dissection, or the like. In thepreferred embodiment, a chamber of a heart 44 is one of the two chambersof the left side of the heart. In the most preferred embodiment, achamber of a heart 44 is the left ventricle.

[0219] Ninth, the channel 50 extending through the entire thickness of amuscular wall 42 can be systematically sized by the passage of standardmeasuring probes. These standard measuring probes, with fixed and knowntip diameters, can be similarly used to size and determine the proximaland distal patency of the coronary artery being bypassed.

[0220] Tenth, through direct and/or thoracoscopic inspection of thecoronary artery lumen 48, or by probing as outlined above, anappropriately dimensioned conduit 10, 10′ of the present invention isselected. As in the case of the open-chest approach (outlined above), anarray of conduits 10, 10′ of various sizes can be available for theoperation.

[0221] Eleventh, either under direct control and visualization, or byindirect manipulation and thoracoscopic viewing, the anchoring arm 12,12′ of the conduit 10, 10′ of the invention is inserted into the formedchannel 50. By similar techniques the remaining intracoronary arm orarms 14, 14′, 16 of the conduit 10, 10′ are seated within the lumen 48of the coronary artery 30 being bypassed. In one embodiment where theprocedure is performed under thoracoscopic viewing, the conduit 10, 10′can be introduced into the cardiac cavity through the space or windowpreviously formed within the anterior inferior aspect of the left chestwall. In this embodiment, the conduit 10, 10′ can be grasped, onceintroduced into the chest cavity, by surgical instruments insertedthrough the trocar sheaths and remotely manipulated into position. Inthis manner the anchor arm 12, 12′ of the conduit 10, 10′ is theninserted into the channel formed 50 via the remote manipulation of theseinstruments.

[0222] Twelfth, the incision present in the superficial wall 38 of thecoronary artery 30 is closed by conventional surgical techniques such assuturing, laser welding, microstapling, and the like. When closure is byindirect thoracoscopic versus direct viewing, suturing, laser welding,microstapling and the like can be accomplished by utilizing surgicalinstruments remotely manipulated following their introduction throughthe trocar sheaths.

[0223] Thirteenth, upon completion of placement of the conduit 10, 10′of the present invention, the heart, if rotated, can be returned to itsnormal orientation.

[0224] Fourteenth, all heart manipulating devices are removed from thechest cavity.

[0225] Fifteenth, contractions of the heart can be allowed to return totheir normal resting rate by the discontinuation of intravenous esmololand diltiazem, if utilized.

[0226] Sixteenth, the pericardium 52 is partially or completelyre-approximated. An external drain can be placed inside the pericardium,as needed, as described by Acuff et al.

[0227] Seventeenth, the trocar sheaths are removed, and all thoracicpunctures surgically repaired in a conventional manner.

[0228] Eighteenth, anesthesia is reversed and the patient revived bystandard techniques.

[0229] E. Embodiments with the Catheter-controlled Approach

[0230] Referring now to FIGS. 10, 11, 12, 13, 14, 15, and 16, anexemplary coronary artery bypass procedure performed throughcatheterization will be described. This approach allows no directvisualization of the coronary vasculature, although the chamber of theheart could be indirectly visualized during the procedure by equippingthe intraventricular catheter with a standard fiber-optic device, ifdesired. Because the procedure is performed through catheters introducedremotely, normal tissue injury is minimized.

[0231] Preparation for the procedure, and anesthesia prior to and duringthe procedure, is outlined above.

[0232] In the embodiment to be described, cardiopulmonary bypass isunnecessary. However, the procedure would be in no way limited ifcardiopulmonary bypass were performed.

[0233] First, an intracoronary catheter 120 (FIG. 10) is inserted via anincision in the groin 126 and advanced within the femoral artery 124.Through continued advancement within the descending aorta 128, and theascending aorta 122, the coronary artery 30 is entered.

[0234] Dependent on the degree of narrowing or occlusion of the coronaryartery, standard angioplasty, atherectomy, or some similar procedure canbe optionally performed if passage of the catheter tip 136 (FIG. 11A) ishindered. Angioplasty, arthrectomy, and the like could optionallyprecede the catheter-controlled bypass procedure.

[0235] If desired, the heart may be slowed while catheterizing thecoronary vasculature, during the construction of a channel or channels50 leading from a chamber of a heart 44 into a lumen of a coronaryartery 30 itself, or both. Such slowing can improve visualization of thecatheters as facilitated by fluoroscopy or the alternative radiologictechniques by which the procedure can be performed. Standardpharmacologic methods, as described above, to slow the heart are wellknown in the literature.

[0236] Second, the intracoronary catheter 120 is advanced within thecoronary arterial vasculature tree to the target location throughstandard catheter manipulation techniques. The proper location of theintracoronary catheter tip 136 in relation to the targeted bypass sitecan be determined through standard radiographic techniques.

[0237] Third, as shown in FIGS. 11A-11C, a balloon 130 located on thedistal end of the intracoronary catheter 120 is inflated (FIG. 11B).Inflation of the balloon 130 causes a stent 134 locatedcircumferentially surrounding the balloon 130 to be seated against thecoronary arterial walls 36, 40. The stent 134 is a hollow expandablestent having a cut-out area 135 along the cylindrical wall of the stent134, for reasons that will become apparent. The stent 134 is positionedat placement within the coronary artery in a manner that the cut-out 135is juxtaposed against the deep wall 40 of the coronary artery 30 uponinflation of the intracoronary catheter balloon 130.

[0238] Fourth, the balloon 130 is deflated (FIG. 11C) and the catheter120 withdrawn into the ascending aorta 122 leaving the expanded stent134 in place.

[0239] Fifth, an intraventricular catheter 140 is inserted into theinnominate artery 144 via an incision in the anterior superior rightchest wall 142 as shown in FIG. 12. The intraventricular catheter 140 isadvanced in a retrograde fashion through the ascending aorta 22, andinto the chambers of the left side of the heart. By continuedadvancement, the intraventricular catheter 140 is extended past thesemilunar valves 148 and into the left ventricle 44. Throughout theprocedure, the location of the intraventricular catheter 140 within achamber of a heart 44 can be ascertained by either indirectvisualization employing standard fiber-optic instrumentation inherent tothe intraventricular catheter, or and/or by standard radiographictechniques.

[0240] Sixth, a channel 50 can be ablated (FIGS. 13A-13B) through both awall of a chamber of a heart 42 and the deep wall of a coronary artery40 utilizing an ablating tip 132. Such ablating devices are well knownin the literature and can include a laser, a radio frequency device, orthe like. Power to the ablating tip 132 can be synchronized via theintraesophageal probe such that ablation occurs at a recurring aspect ofthe cardiac cycle. Such synchronization of devices to physiologicalfunction is well-known in the literature. The ablation can be indirectlyobserved via fiber optics associated with the intraventricular catheter140. Alternatively, the location of the ablating tip 132 can bedetermined by standard radiographic techniques.

[0241] Seventh, once a channel 50 through the heart chamber wall 42 isformed, the intracoronary catheter 120 is re-advanced into the coronaryartery 30.

[0242] Eighth, the balloon 130 on the distal end of the intracoronarycatheter 120 is re-inflated upon reaching the target bypass site, asillustrated in FIGS. 14A and 14B. Inflation of the intracoronarycatheter balloon 130 seals the formed channel 50 so that blood isprevented from flowing from the coronary artery lumen 48, through theformed channel 50, and into a chamber of the heart 44. Note, though,that the inflation of the intracoronary catheter balloon 130 stillallows blood to perfuse the downstream portion of the coronary artery30. This is because the intracoronary catheter 120 is equipped withchannels 138 which allow blood to pass internally within theintracoronary catheter 120 from the upstream portion of the coronaryartery 30, and to exit the catheter into the downstream portion of thecoronary artery 30.

[0243] Ninth, the ablating catheter 140 is removed from the bodycompletely.

[0244] Tenth, a second intraventricular catheter 160 is inserted intothe innominate artery 144 at the arterial cut-down site 142, as shown inFIG. 12. The intraventricular catheter 160 is next advanced in aretrograde fashion into the ascending aorta 22. By continuedadvancement, the intraventricular catheter 160 is finally extended pastthe semilunar valves 148 and into the left ventricle 44.

[0245] This intraventricular catheter is equipped with a inflatableballoon 60 on the catheter's distal end, and a stent-forming device 61circumferentially surrounding the balloon 60 on the catheter's distalend (FIGS. 14A-14D).

[0246] The stent forming device 61 is a spiral sheet shown separately inFIGS. 15A and 15B. Initially, the device 61 is a sheet formed in aspiral shape as shown in FIG. 15A to present a reduced diameter smallerthan the diameter of the formed channel 50. In response to expandingforces (e.g., expansion of a balloon 60 within device 61), device 61expands to a cylinder as shown in FIG. 15B. Interlocking tabs 61 a andrecesses 61 b on opposing edges of the device 61 define a lockingmechanism 62 to retain the device 61 in a cylindrical shape. Thecylindrical shape of device 61 after expansion of the balloon 60, asshown in FIG. 15B, is larger in diameter than the spiral shape of device61 prior to expansion of the balloon 60, as shown in FIG. 15A. Thedevice 61 as expanded is sized to be retained within the formed channel50 upon expansion.

[0247] Throughout this portion of the procedure, the location of thissecond intraventricular catheter 160 within a chamber of a heart 44 canbe ascertained by either indirect visualization employing standardfiber-optic instrumentation inherent to the second intraventricularcatheter, or and/or by standard radiographic techniques.

[0248] Eleventh, the tip 180 (FIG. 14A) of the second intraventricularcatheter 160 is introduced into and advanced within the formed channel50.

[0249] Twelfth, with the tip 180 of the second intraventricular catheter160 near or abutting the side of the intracoronary catheter balloon 130,a balloon 60 surrounding circumferentially the tip of the secondintraventricular catheter 160, is inflated. As shown in FIGS. 14C and14D, inflation of the balloon 60 causes the device 61 locatedcircumferentially around the balloon 60 located on the end of the secondintraventricular catheter 160 to become seated against the walls of theformed channel 50.

[0250] As shown in FIG. 16, the device 61, is locked into thecylindrical position when the underlying balloon 60 is inflated by aninterlocking mechanism 62 constructed as part of the device 61.

[0251] Thirteenth, the balloon 60 on the intraventricular catheter tipis deflated, and the catheter removed from the body, as shown in FIG.14D.

[0252] Fourteenth, a third intraventricular catheter 70 is inserted atthe innominate artery access site 142. This third intraventricularcatheter 70 is then advanced in a retrograde fashion into a chamber ofthe left side of a heart, as outlined above.

[0253] This third intraventricular catheter 70 is equipped with a hollowtube 71 on its distal tip which can interlock to the device 61previously placed within the formed channel 50, as shown in FIGS. 17Aand 17B.

[0254] Fifteenth, the hollow tube 71 is forwarded within the formedchannel 50, and interlocked to the device 61. In one embodiment, thehollow tube 71 can partially insert into the device 61 previously seatedwithin the formed channel 50.

[0255] The hollow tube 71 can, but may not necessarily, be equipped witha bi-directional flow regulator 74 to provide full blood flow in thedirection of arrow C with reduced (but not blocked) blood flow oppositethe direction of arrow C. An array of such hollow tubes 71 of variousdimensions can be available to the surgeon at the operative procedure.

[0256] Sixteenth, the balloon 130 on the end of the intracoronarycatheter 120 is deflated.

[0257] Seventeenth, angiographic dye can be introduced into a chamber ofthe heart through a port internal to the third intraventricular catheter71. The introduction of angiographic dye can allow the blood flow to bevisualized under fluoroscopy, digital subtraction angiography, orsimilar standard techniques. By such radiographic examination, bloodflow directly from a chamber of a heart into a coronary artery can beascertained. In cases where a bi-directional flow regulator 74 isutilized, the bi-directional flow from a chamber of a heart and into acoronary artery and the flow rates can be verified.

[0258] Eighteenth, the third intraventricular catheter 70 is withdrawnfrom the body through the innominate incision site 142.

[0259] Nineteenth, the intracoronary catheter 120 is withdrawn from thebody through the femoral incision site 126.

[0260] Twentieth, the sites of the innominate incision 142 and femoralincision 126 are surgically re-approximated through standard closuretechniques.

[0261] Twenty-first, anesthesia is reversed and the patient revived bystandard techniques.

[0262] Changes and Modifications

[0263] Although the foregoing invention has been described in detail byway of illustration and example, for purposes of clarity ofunderstanding, it will be obvious that changes and modifications may bepracticed within the scope of the appended claims.

What is claimed is:
 1. A method for revascularizing a coronary vesselfrom a heart chamber with a conduit through a heart wall, the conduitincluding a first end and a second end, the conduit defining an innerdiameter transition that narrows as the transition extends from thefirst end toward the second end, the method comprising the steps of:forming a blood flow pathway from the heart chamber through the heartwall and into the coronary vessel; placing the conduit in the blood flowpathway with the first end of the conduit proximate to and in fluidcommunication with the heart chamber and the second end proximate to andin fluid communication with the coronary vessel, the first and secondends in fluid communication; and directing blood flow through theconduit from the first end to the second end.
 2. The method of claim 1,wherein the blood flow pathway remains open during both systole anddiastole.
 3. The method of claim 1, wherein the inner diametertransition forms a venturi restriction within the conduit.
 4. The methodof claim 1, wherein the conduit is placed in the blood flow path so thatthe first end extends into the heart chamber beyond the heart wall. 5.The method of claim 1, wherein the inner diameter transition terminatesat a minimum inner diameter at a point proximate the second end withinthe conduit.
 6. The method of claim 1 wherein the inner diametertransition terminates at a minimum inner diameter at an intermediatelocation between the first and second ends and a second inner diametertransition from the minimum inner diameter toward the second end isdefined which enlarges as the transition extends from the minimum innerdiameter toward the second end.
 7. The method of claim 6, wherein theinner diameter transition defines an angle with respect to a centralreference axis of the conduit that is greater than an angle defined bythe second inner diameter transition with respect to the centralreference axis.
 8. A method of revascularizing a coronary vessel of apatient comprising the steps of: providing an implant including: amyocardial leg including a first end and a second end and defining aconduit between the first end and the second end, the conduit includinga maximum cross-sectional area proximate the first end and a point ofminimum cross-sectional area; a vessel leg with an outflow end andincluding an open conduit which cooperates with the second end of themyocardial portion to provide fluid communication between the first endof the myocardial leg and the outflow end of the vessel leg; forming apassageway from a lumen of the coronary vessel through a myocardium ofthe patient to a heart chamber; placing the transmyocardial implant intothe passageway so that the first end of the myocardial leg protrudesinto the chamber of the heart, the myocardial leg extends through thepassageway to the vessel, the vessel leg is axially aligned with thelumen and placed within the lumen, and the outflow end of the vessel legis in fluid communication with the lumen of the coronary vessel; anddirecting blood flow through the implant from the first end to thesecond end.
 9. A transmyocardial implant comprising: a myocardial legincluding an open conduit providing fluid communication between a firstand a second end, the open conduit defining a diameter, the conduitdefining a minimum diameter at least at one point within the conduit,the first end having a diameter greater than the minimum diameter, andthe conduit defining a smooth transition from the first end to the pointof minimum diameter; a vessel leg including an open conduit with anoutflow end, the open conduit of the vessel leg in fluid communicationwith the open conduit of the myocardial leg through the second end ofthe myocardial leg; and the transmyocardial implant sized to be placedwithin a myocardium of a patient so that the first end protrudes into aheart chamber of the patient, the vessel leg lies within a lumen of acoronary vessel of the patient with the outflow end in the direction ofnormal blood flow, so that the open conduits of the two legs cooperateto provide a blood flow pathway from the heart chamber into the lumen ofthe coronary vessel.
 10. The transmyocardial implant of claim 9, whereinthe open conduit remains open during systole and diastole of the patientwhen the transmyocardial implant is placed in the heart of a patient.11. The transmyocardial implant of claim 9, wherein the point of minimumdiameter of the transmyocardial leg is proximate the second end.
 12. Thetransmyocardial implant of claim 11, wherein the first end defines apoint of maximum diameter.
 13. The transmyocardial implant of claim 9,wherein the point of minimum diameter is located intermediately betweenthe first and second ends.
 14. The transmyocardial implant of claim 13,wherein the first end defines a point of maximum diameter.
 15. Thetransmyocardial implant of claim 14, wherein the open conduit of themyocardial leg has a diameter at the second end which is greater thanthe minimum diameter and the open conduit of the transmyocardial legtransitions smoothly from the point of minimum diameter to the secondend.
 16. The transmyocardial implant of claim 15, wherein the transitionfrom the first end to the minimum diameter makes a greater angle withrespect to a central reference axis of the transmyocardial leg than thetransition from the second end to the minimum diameter.
 17. Thetransmyocardial implant of claim 9, wherein the vessel leg includes ainflow end opposite the outflow end, the open conduit of the vessel legprovides fluid communication between the inflow end and the outflow endand the second end of the myocardial leg provides fluid communicationbetween the open conduits of both legs at a point intermediate betweenthe inflow end and the outflow end.